Balancing machine



sepf. 14, 1941s.`

T. C. VAN DEGRIFT ETAL.

BALANCING4 MACHINE l1 Sheets-Sheet l Filed De. 8. 1945 SPf- '14, 1948- T. VAN DEGRIFT l-:TAL 2,449,429

BALANCING MACHINE Filed Dec. 8. 1943 A. 11 sheets-sheet '2:

Bl www M Y' attorneys Sept 14, 1948. l T. c. VAN ADEG-RIFT ET AL 2,449,429

BALANCING MACHINE 11 sheets-snaai s Filed Dec. a. 1945 Inventors Sept. 14, 1948.- Tl c. VAN DEGRIFT Erm. 2,449,429

` "BALANcmG Incarne l Fled'Dec. 8. 1943 11 Shoots-Sheet 4 Sept. 14, 1948. T. c. vANpi-:GRIFT ETAL 2,449,429

' BALANCING MACHINE Filed Dec. 8,1945 11 Sheets-Sheet 5 l Gttorncg-f T. c. VAN DEGRIFT Erm. 2,449,429

BALANCING MACHINE 11 Sheets-Sheet 6 Sept. 14, 1948.

Filed nec. 8. 143` Rm mw \M e 8u @zaz' Zmaa www Gttomeg-f Sept 14, l948.l T. c. VAN DEGRIFTErAL BALANS ING MAQHINE 11 Sheets-Sheet '7 Filed Dec. 8. 1943 Sept, 14, 1948. T. c. VAN DEGRIFT ETAL. 2,449,429

' BALANCING MACHINE l Filed nec, 8, 194s l 11 'sheets-sheet e attorneys sep; 14, 194s.

Filed Dec. 8, 1945 m.,ll 2 if?" Se) T. C. VAN DEGRIFT ETI" Al.`

BALAHCING Imprime 11 Sheets-Sheet 9 Sept. 14, 1948.

Filed Dc. 8, 1943 T. C. VAN DEGRIFT ETAL.

BALANCIG MACHINE.

l1 Sheets-Sheet 10) Sept. 1 4, 1948,' 1'. c. vAN DEGRIFT Erm. 2,449,429

' Bmcms MACHINE v Filed Dea. 8, 1943 11 Sheets-Sheet 11 BB Mzzl Patented Sept. 14, 1948 UNITED STATES PATENT GFFICE 2,449,429 BALANCING MACHINE Thomas C. Van Degrii't, Andrew W. Zmuda. and

- Earl F. Riopelle, Detroit. Mich., assignorl to General Motors Corporation. Detroit, Mich., a

corporation of Delaware Application 'December 8, 1943, Serial No. 513.420

vcorrect any small amount of unbalance remaining after the completion of the rough balance.

while they are freely rotating in the machine and in the rough balancing operation (at a speed of about 1800 R. P. M.) experience has taught that it is inadvisable to attempt to correct for all o! the unbalance. I operation (at a speed o! about 5,000 R.. P. M.) is

The lout-oibalance of the rotors is determined 1u 1o claim. (ci. zr-21) Van Degrift 2,293,371) which partakes oi the same movement as the body to be balanced, i. e., the rotor.

Another novel feature 'of the invention is'the supplying of a constantY flow of lubricant to the plain bearings ofthe finish balance. constantly feeds filtered lubricant because any roughness in the bearing will have an effect on the indication of the amount of unbalance.

A further novel feature of the invention is the provision in the machine of two drills to drill the rotor to remove metal to bring about true balance.

A second er finish unbalance 1:,

necessary to obtain the fineness and accuracy of balance desired i'or the rotor. For the rough balance the shaft oi the rotor operates in ball bearings which rest freely on a curved .track in 2 a pendulum suspension member. For the iinish balance the rotor 'shaft is mounted in plain bearings made of high lead bronze supported in a4 Neoprene suspension member.

The vibration orv motion o! the plain or roller 2 bearings caused by the unbalance is communicated to a Brush DP-l displacement, piezoelectric type -pickup, and the` action on the pickup is communicated to a Model 160-B RCA (Radio Corporation of America) oscillograph as the ver- 3 tical input. The sweep of the light spot on the fluorescent screen of the oscillograph is controlled by a voltage impulse on the grid; of the oscillator tube of the sweep circuit of the oscillo- On the drawings: Figure l is a front elevation oi the novel balancing machine with the set-up for the finish balance.

Figure '2 is a side elevation of the machine of Figure 1.

Figure 3 is an enlarged sectional view ofthe central part of the machine showing the iinish balance setup with the rotor in dotted outline. 'Ifhe view is taken on the line 3-3 of Figure 2.

Figure 4 is an enlarged detailed end view o! thetrack taken Von the line 4-4' of Figure 1.

Figure 5 is an enlarged detail view of the drills 'and their mounting and of the drill stop. i

Figure 6 is an enlarged detailed view of the the line 0-8 stop.

pulse on the grid oi the oscillator tube of the an indicator bar or nodal bar (see the patent to Figure 9 is a detailed view substantially on the line 8-9 oi' Figure 8. Figure 10 is a side elevational view of the finish balance setup oi a structure using an indicator bar. i

Figure 11 is a front elevation. partly in section, showing the rough balancing construction with an indicator lbar from which the unbalance is measured. The view is taken on the line Il-Ii of Figure 13.

Figure 11a is a detailed view on the lirl'e lia- Ila of Figure 11. showing the manner` of lremovably mounting the indicator bar in Figure 1'1.

Figure 12 is a viewl similar to Figure 3. but showing a different type and shape of rotor.

Figure 13 is a side view of Figure 11 taken on the line i3-I3 of Figure 11.

Figure 14 is a view similar to Figures 3 and 11,

A pump but showing a dierent 'type and shape of rotor and taken on the line |4|4 of Figure 10.

Figure 15 is a plan view of the indicator bar and its mounting of Figure 10. taken on the line V ll--Il of Figure 10.

Figures 16 and 17 are detailed-sectional views on the lines |4|8 and |1|1 of Figure 15.

Figure 18 is a front elevational view. with parts shown in section, of the rough balance setup for a di'erent type of rotor.

Figure 1 9 is a plan view of the indicator bar of Figure 18 and its mounting. parts being broken awayvclearer to illustrate the construction.

Figure 20`is a side view on rthe line 20-28 of the structure of.Figure 18.

Figure 21 shows so much of the wiring diagram of the oscillograph as it diil'ers from the convento oil inlet and oil outlet iittings 82 and 84 in an oil header 88 rigidly mounted on the adapter support 28.

The suspension assembly i is substantially the same as the suspension assembly I2 except that it is not rigidly mounted on the sub-base t but is shiftable along the track I8. An adapter support 88 is rigidly secured to the adapter plate 22' and this support has an extension 10 extending over the track I8 and serving as a mounting for the right hand' oil header 88. The lower part of the support 08 is shaped as at 1| (Figure 4) to conform to the dovetail shape of the track I8 and a gib 'l2 is placed between the dovetaii track I8 and the shaped lower part Il to take up play.

, Suitable oil inlet and outlet connections 14 and 18y (see Figures 1 and 4) are secured to the header 88' and pass through an opening 18 in the track and a slot 88 in the sub-base. The extension 'i0 has a cover plate 82 secured thereto to protect the duck ways 84 which are formed of "Bakelite" or material treated therewith and which are secured to the trackI8.

assemblies I0 land 2, better shown in detail in Figure 3. The rotor I4 to be balanced is mounted by its shaft i8 in the suspension members. The left hand assemblyi 2 (Figures 1 and 3) is rigidly mounted on the sub-base 8 while the right hand assembly I0 is slidably mounted as a unit on a track |8 (Figures 2 and 4) to enable the insertion `and removal of rthe rotor I4 and its shaft I8.

Referring to Figure 3, the suspension assembly l2 comprises the central chucking ring 20 supported in the outer adapter plate 22, the lower end 24 of which is positioned on and rigidly secured to the adapter support 28 which in turn is rigidly secured to the sub-base 8. The chucking ring has an eccentric opening 28 in whichrthere is positioned the suspension member 28 which is used for the finish balance only. 'Ihis suspension member comprises an outer ring 80, an inner ring 22 and a washer-shapedl filling 24 of synthetic rubber, such as Neoprene, therebetween. The "Neoprene is vulcanized to both rings. When the rotor i4 is in position in the machine, the weight of the rotor will compress the Neoprene somewhat to cause a slight sag in the Neoprene." A dowel pin It enters an opening in the chucking ring .and 'a recess in the outer ring 30 of the suspension member to position the suspension member and to prevent its rotation. The opening 28 ,is suinciently large to enable the insertion of the suspension member 28 and its positioning over the pin 88. To hold the suspension member laterally,

an outer cover plate 38 and an inner stator sup-y port 40 are removably secured to the adapter plate 22. The stator support has rotatably mounted thereon a circular dial or index 42 graduated in 360. To the top of the adapter plate a pointer or index ilnger 44 is secured. The pointer 44 extends over the dial and closely adjacent the side face of the outer part of the rotor.

At the center oi' the suspension member 28 a bearing housing 46 is rigidly secured, and in the housing 48 a plain bearing 48 for the shaft I8 of the rotor is positioned. Aninner oil retainer 80 and an outer bearing cap 52 are secured to the bearing housing 46. The cap 52 has an axial oil A handle 88 at the front of the machine operates a mechanism (not shown) to lock the support 88 to the track I8. The handle is shown in the locked position of the mechanism in Figt ures 1 and 3. By swinging the handle, counterclockwise the mechanism is released, thereby enabling the adapter support t8 and the parts secured thereto to be shifted to the right on the track I8.

The adapter plate 22 has a stator support 48' secured to the inside thereof. A stator 88 is secured to the stator support 40' by the bolts 80 and a stator92 is secured to the stator support 40 by similar bolts 90. The center of the rotor ll'has recesses at both sides which enable the stators to extend part-way into the rotor but out of contact therewith. Wires 84 from a source of electric energy (in4 this instance a variable frequency unit) lead to the stators 88 and 82 to energize the same and cause the rotor i4 and its shaft I6 to turn in the bearings 48. The base 4 houses a lubricating system to deliver oil to the headers 88 and 66'. An oil reservolr, having a illler spout $8. a vent |00 and a drain |02, is mounted in one comer of the base inlet opening in which the oil inlet tube 54 is 4. The reservoir 06 has an outlet pipe |04 havvoir 96 while another outlet ||8 delivers oil to the top of a lter I8. The oil passes through the ltering material in the filter and leaves the filter at the bottom through the T connection |20. From the connection |20 the oli passes through the oil resistant flexible tubing |22 to the oil headers 68 and 68'. From the oil headers the oil passes to the inlet pipes 54, into the bearing caps 52, then between the journals of the shaft i8 and the bearings 48 and into the oil retainers 50. The oil then passes through an opening |24 in each bearing housing 48 and into the outlet pipes 56 and then through the headers 66 and 66' into the oil resistant return exible tubes |26. From the tubes |26 the oil returns through the pipe |28 to the reservoir 96. The pump |08,A bypass ||2 and filter have a resistance such as to make an oil pressure of four or fivepounds at the bearings 48.

The pressure is just suillcient to keep a slow flow of oil passing through the oiling system. i

The oiling or lubricating system .is used in connection with the finish balance only and its purpose is to obtain a free and easy rotation of the rotor during the balancing -operation. Any roughness in the bearing. or any particle of foreign matter, will cause a Jiggling action and prevenil a smooth curve from being obtained on the osclllograph screen.

The out-of-balance movement of the rotor i4 and its shaft I8 are communicated to two Brush DP-l displacement piezoelectric type pickups |80 mounted on the adapter plates 22 and 22'. The mounting is best shown in Figure. Suitable electric connections (not shown) pass through an opening |3| to transmitthe electric chargev developed at the surfaces of crystal to the -oscillograph. A detailed description of the inside of the pickup is not given for the-reason'that it forms no part of the invention and the pickup is purchased commercially.

The pickup support is indicated at |82. This support comprisesbase member |84 and the two steel tubes |38 secured thereto. Suitable long bo1ts,ithe knurled heads of which are indicated at |38, pass through the steel tubes I|38 andare screwthreaded into the adapter plates 22 or 22'.

The Neoprene 34 has an opening |40 therein and a needle-like probe |42 extends through the opening |40 and through a mating opening- (not shown) in the adapter plates 22 and 22. The

` probe |42 has a point which is pressed against thumb screw |84 screwed into the adapter |52 holds the pickup on the pickup support |82.

The oscillograph |12 (Model 16'0B, five-inch RCA) is rigidly mounted at the back center of the machine on a box-like support |14 secured to the base 4. The screen of the oscillograph is indicated at |18.

When the place andamount of unbalance are determined, drills |18 are provided-to remove the necessary amount of metal. The drills are driven by electric motors |80 and the drills and motors are mounted on supports |82 secured to hinge blocks |88 pivoted between the ears |84 of brackets |88 rigidly secured by bolts and nuts |88 to a shelf |90 at the rear of the sub-base 8;

' Handles |9| operate a conventional rack and pivoted at |94 in a bracket |95. The pivotalv axis at |94 is coincident with the pivotal axis of the brackets |82. This drill stop is generally H-shaped and is pivoted at the two lower arms of the H while the two upper arms are capable of straddling the rotor. The arms of the drill In the structure of the finish balance of Figures 1-4, inclusive, and 6, the pickups are able to take the unbalance directly from the bearings in the adapter plates. The inherent distribution of mass of the rotor indicated in Figure 3 lpermits this, but rwith diierent shaped rotors the pickups cannot be mounted at the adapter plates because it is impossible to pick up the unbalance at the bearings.

In order to assure that the wave on the oscillograph screen always will start at `0" on the screen scale, the triggering structure of Figures '1 and 21 is provided. The adapter support 88 at the right side has a housing |58 at its upper part and this housing is covered by a cover |88. The housing |58 has one side open at |80 and this opening |80 mates with an opening |82 in the lower part of the adapter plate 22'. The rotor in its rotation passes in front' of the openings |62 and |80 and has a painted or bright spot thereon which passes the openings once each revolution. In the housing there is mounted a small electric light bulb |84. This bulb |84 is mounted in a tube |88 which has a lens |88 mounted in the end thereof. The beam of light is focused on the side of the rotor by adjusting the position of the tube |88. The beam will fall on the rotor side in the path oi. the bright spot. The reilected beam of light from the bright spot strikes a light `sensitive cell |10 mounted in the housing |88. The current produced by the light falling on the cell |10 is transmitted by suitable wires f. (not shown) to the circuit of the oscillograph.

stop are spaced sufficiently wide to take care of the thickest or widest roter, but to accommodate the stop to a narrower rotor. illler blocks are secured at the insides of the arms of the H, openings l95 being provided to secure the blocks in place. These filler blocks are of sufficient width to enable a rotor to be snugly received between them. When the drill stops are in operative position the arms thereof back the rotor in line with the drills to enable the drills to remove an amount of metal equivalent to the unbalance.

The drills |18 are graduated to tell the operator how far to operate them to remove a given amount of metal.

The brackets |82 for the drills |18 each have extension lingers |93 which engage the drill stop |92 to -move it upwardly on its pivotal axis |94 to cause the arms thereof to be positioned on opposite sides of the rotor. A spring |98, having its ends secured to the drill stop and to the mounting bracket |86 for the drill stop. pulls the drill stop away from the machine or to inactive position when the drills are moved to inactive position. i

A switch |98 is mounted in the rear of the machine. This switch has an operating arm |99 in the'path of the drill stop |92 and when the drill support brackets |82 are moved tothe position shown in Figure 1, they move therewith the stators and driving the rotor when the. drills are operating.

Referring to Figure 8, brake blocks or shoes '200 covered with hard vfelt 202 are provided to stop the rotor I4 after the outofbaiance has been determined. The shoes are pivoted at 208 to brackets 204 rigidly mounted on the upper end of rods 208 which extend through `openings in the sub-base 8. The brackets 204 normally rest on the machined surface 8. The rods 208 are pivoted at 208 to the ends of a brake beam 2|0 which has pivoted at its center a brake rod 2|2, the lower end of which is pivotally connected at 2 |4 to a treadle or foot pedal 2 8 pivotally mounted at 2| 8 to a bracket 220 secured to the base 44 (Figure 2). Suitable springs 222. 224, and 228 Because the frame. |82 of :guano 236 always urges the track section 226 downwardly. The lower end of the rod 236 is pivotally secured at 233 to the end of a lever 232, pivoted at 228 to a bracket 236 secured to the sub-base 6. The handle of the lever 232 extends outwardly of the sub-base through an opening in the sub-base and has a short locking lever 234 pivoted thereto. ,The lever 234 has an integral `downwardly extending hook 236 adapted to engage under a latch 233 pivoted at 240 to the subbase 6. Two latch adjusting blocks 242 and 244 are secured to the sub-base 6 and adjusting screws 246 are screwed into the blocks. Nuts 24| retain the screws 246 in adjusted position. The purpose ofthe fine adjustment made possible by the structure of Figure 8 is to enable the operator to adjust the position of the movable track section sothat the shaft of a rotor carried by it is in very accurate alignment with the bearings 46 in the suspensions 36.

The operation of the structure of sheets I-6 is as follows: The operator will first move the handle 66 to release the movableA adapter support 68. The support 68 and connected mechanism is then moved on the track I6 toward the end o1' the machine. A rotor is now placed on the duck ways 84 and -the rotor is then slid on to the 'ways 84' which at this time are in their dicatethe amount of unbalance and the position on the scale of the upper peak oi' -the curve will indica-te the place of unbalance. The rotor is now stopped by the brakes.

After the amount and place of unbalance are determined. the operator presses .the foot pedal in the stationary suspension members 28 as shown at the left of Figure 3. The shiftable adapter support 68 and its adapter pla/te 22' are now shifted toward the rotor until the suspension member and its bearing 46 are properly positioned on the shaft of the rotor.' The handle 66 is now moved to locked position and the hook 236 released from the catch 236 to enable the movable track section to drop away from the rotor I4. The drills |18 -and the drill stop |92 are away from the rotor. The 4electric current is now turned on to energize the stators which will cause .the rotor vto rotate. When the desired degree of speed has been reached, the power is shut oil and the rotor allowed to run freely, and during this free rotation the unbalance isv noted. The wobbling` or the vibration of the rotor due to unbalance will compress the Neoprene and also move the probe |42 to affect the pickup |30.` The electric charges produced in the pickup will be recorded as vertical displacements in the curve depicted on the screen of the oscillograph. Each time the bright spot on 4the rotor passes the light |64. the cell |10 will be ailected and the produced electric current transmitted to the circuit of the oscillograph to cause the spot of light from the cathode tube to be started at 0 on the oscillograph scale and traverse the scale once. The graph on the screen will have the shape of a sine curve and the verti-I cal distance between peaks of the curve will in- 2|3 to stop the rotor. The rotor is -then removed and a new one inserted. y

The -dial' 42 and rotor I4 are now relatively oriented so that the 0 mark on the dial corresponds with the bright spot on the rotor. By now observing the number of degrees on the dial corresponding to the degrees on the oscillograph corresponding to the upper peakof the sine curve. the place of unbalance on the rotor is indicated.

.This piace is marked. The drills and drill stop are now swung into place and the motors |36 operated --to turn t-he drills. By moving the handle (or handles) |6|, the drill can be moved to the rotor to cause the proper amount of metal to be removed.

Figures 11 and 13 show the, rough balancing `setup and opera-tion corresponding to the ilnish balance setup of Figures 1-9 inclusive. As much of the structure of Figures 1-'9 inclusive is omitted which would be duplicatedfor the rough balancing operation and the struct-ure shown is that which is different from Figures l-9, inclusive.

In this rough'balanclng operation, the pickup points or places do not coincide with the bearings and itis necessary to use anauxiliary device such as an indica-tor bar or nodal bar 246 to enable the pickups to register the degree of unbalance. The probes |42' are applied similarly as the probes |42 are applied in connection with the ilnish balancing operation, except that they are attached at their outer ends to the indicator bar. A yoke 266 is secured to one .probe and two pointed pins 262 are screwthreaded into the arms of the yoke and are plvoted in recesses in the bar 246. The other probe at the other bearing of the rotor is secured to a member 263 having a knife edge 26| which rests against the inside of a wear band 266 which surrounds the bar. lA flat spring 261, having its outer end upwardly curved to bear against the outer side of the bar and pressv it again-st the knife edge, is secured tothe bottom of the knife edge member. In this way one end of the `par is removably secured to permit its being moved so 4that the movable assembly can be shifted to remove a rotor and replace it with another. A spring 266 constantly urges the probeI |42.' against the bearing 262 of the rotor.

The antifriction ball or roller bearings 262 used in the rough balance setup are allowed to yeid in the horizontal plane only, and for this rough balancing operation the suspension members or suspensions 28 are removed from the suspension assemblies i0 and |2 and the rough balance or pendulum suspension 264 substituted therefor. 'I'his rough balance suspension 264 comprises a ring 266 which fits in a centraiizing ring 266 which in turn fits snugly in the eccentric openings 23 of the- The ring 266 has a bearing retainer 214 secured thereto. and this retaineryhas an arcuate track 216 on which the bearing 262 rests. The retainer is also provided withal stop plate 211 to serve as an -abutment for thev bearing when the rotor is .placed in position. A switch actuator linger or 9 Y bracket 219 is secured to the bearing retainer and when the rough balancing setup is in place the actuator 219 contacts the button 218 of the limit switch 280 which controls a double throw contactor for supplying either .the high frequency or low frequency power to the stator. Figure 11 shows the rough balance setup which requires 1l0-volt, 60-cycle, 3-phase power to the stator to drive the rotor at the approximate rough balan-ce speed of 1750 R. P. M. When the switch 280 is actuated by the finger 219, the power to the oil pump motor and to the frequency changer drive motor is cut out.

Because the points at which the out-of-balance is to be taken by the pickups |30 do not coincide with the bearing supports in the adapter plates 22 and 22', it is necessary to determine two newplaces or points at which to apply the pickups: If we take a rotor known to be in perfect balance, apply an unbalanced weight in the .plane of one of its lateral faces, then rotate the rotor in the balancing structure of Figure l or Figures 11 and 13v and later allow the rotor to run freely with the power shut off from the stators, it will be found that the indicator bar will have a place where there is no vibration, that is, a node, in a plane parallel tothe rotor face and spaced from the other side of the rotor. If the vprocedure is repeated with the weight transferred to the other face of the rotor, a second node will be found in a plane spaced from the rotor side which does not have the weight applied thereto. The out-of-balance of the rotor in the` rough balancing setup is taken at these nodalv points which are suitably marked on the indicator bar.

The pickup |30 of Figure 10 is mounted on a pickup support 282 which has a hinged top 284 held in place by a pivoted eye bolt and knurled nut 288. The pickup has a. probe 283 adapted to contact the nodal bar 249 at the nodal points. The support has the weighted bottom 209 (see Figure which rests ilatwise on the machined surface 8 and is manually movable to adjust the support to the desired position so that the probe 288 will be at the'nodal point which has previously been determined and marked on the nodal bar.

Figure 12 is a view similar to Figure 3 and shows the finish balance setup for a rotor 4|, which is different from the rotor |4 of the Figures 1-8, inclusive. In this species but one stator 92a is used. The stator support at the right is replaced by the plate 292 and the stator support 40a at the left is differently shaped to accommo-` date it to the length of the rotor shaft |8a. The rotatable'annular index or dial 42' is secured to the stator support adjacent the rotor and the pointers 44a and 44h are shaped slightly differently. The oiling system'l the installation of the pickups |30, and the rest of the structure is the same as shown in Figures 1-3 and 6.

Figure 14 is also a view similar to Figure 3, and shows the finish balance setup for a still different type of rotor I4". In this species, as in Figure 12, but one stator 92D is used, and the stator support 40b is'diiierently shaped to accomlmodate it to-the rotor and the rotor shaft.' The bearing 48a is also differently shaped toaccommodate it to the shaft |8b. The main difference between the showing of Figure 14 and its related Figures 15--17 over Figures 3 and 6 is in the application of. a nodal bar 249. Each adapter support 22 or 22' has a bracket 300 secured thereto by suitable clamp screws (see Figure 10) and on the ends of these bracketsthere are rigidly mounted the extensions 302 and 303. Each extension has pivoted thereto at 304 a. lever 308 or 301 and the nodal bar `249 is mounted at the free ends of these levers. The mounting for the nodal bar at the right hand lever .308 is shown in..

detail in Figure 17. The lever 308 has a reduced end 308 flat on the side toward the lnodal bar 249. A spring 3|0 is pivoted at its ends to the nodal bar by means of the screws 3 2. This spring 3|0 has a loop 3|4 at its end adapted to be removably engaged with the end 308 of the lever 388. A roller 3|9 is mounted in the nodal bar, and this roller bears against the flat face 'of the lever 308- By swinging the spring' 3|0 on its pivots to the left (Figure 15) the adapter sullport 22' is disengaged from the nodal bar and can be moved to enable the withdrawal of the balanced rotor and replacement by an unbalanced One.

, urge` 'the levers 308 and 301 against the ends of the probes.

The support for the nodal bar from the lever 301 is shown in detail in Figure 16. A fork or yoke 320 has a shank 322 journaled in the lever 301. The nodal bar is received in the fork of the yoke 320 and a pin 324 passes through the tines of the fork and through the nodal bar to form a pivotal connection. When the loop 3|4 is freed from the end 308, the nodal bar 249 can be swung gaiits pivot formed by the shank 322 in the lever The linkage for the nodal bar shown in Figure 15 is an amplitude increasing linkage better to enable the nodal bar to communicate to the pickup |30 the small amount of out-of-balance.

Figures 18, 19 and 20 show a rough balance setup and unique nodal barmounting for `a still different type of rotor |4"' using but one stator 92. If a nodal bar mounting such as shown in Figures 10 and 11 were used, a very long nodal bar would necessary because the nodal points occur at .much vwider spaced places. To decrease the length of the nodal bar, an Aamplitude decreasing linkage as shown is used. Brackets330 are secured to the adapter pla-tes 22 and 122 by means of the screws 332.` Each bracket has a bore to enable the passage of the probe 334, and

also hasV secured thereto an inwardly directed end at 346 to the end of the arm 338. The lever` 344 is somewhat zig-zag shaped and has a part 348 which extends under and parallels the indicator bar 249. A pivot pin 380 enters a slot 38| inthe indicator bar. The ends of the probes, 334 act on the free ends of the levers 340 and 344, and tension coil springs 382, secured at their ends to the levers 340 and 344 and brackets 330, always maintain the lever ends in contact with the probes 334 and the Probe ends in contact with the bearing. A support 384 is journally mounted in the lever 340 and a fork 358 on the end of the support receives the nodal bar 249 therebetween. 'I'he nodal bar 249 is supported at opposite sides by pivot pins 388 having points fitting in corresponding indentations in the bar. Compare Figures 1l and 13.

Referring to Figure 20, there is shown in side view the rough balance setup for the rotor II'" having a smaller bearing 262. The suspension assembly 264' is shaped differently but has the inclined or arcuate track 218' and there is secured to the assembly 284' the metal strip 36| to serve as an abutment for the en'd of the rotor shaft and the bearing. Screws 210' arel provided to prevent the rotor M'" contacting the stator when the -power isron. Clearance as shown at 212d is allowed between the ends of the screws 210' and the bearing 282' to enable the rotor il'" to run freely immediately after the power is shut oiT the stator in order that the unbalance can properly be indicated to the pickup by the probes I and the indicator or nodal bar 249.

` Figure 21 shows only so much of the oscillograph circuit as is different from the conventional circuit of the RCA No. 160B osciliograph.

The operation of the phototube synchronizer circuit is as follows: The purpose of this circuit is to lock the sweep of the oscillograph in phase with the rotation of the part being balanced. In order to do this. a voltage must be impressed on the grid of the RCA-884-V4 tube of the oscillograph at the proper time. This is accomplished in the following manner:

A bright, light-reflecting'spot is put on the part to be balanced. This reflecting surface is used to reflect the light ray from a source |84 through a lens |88 to a phototube |10 eachtime the spot passes the light ray as the piece is being rotated in the machine. Thus, by the nature of the phototube |10, an implse of current is permitted l to iow each time the light is received. This impulse of current also results in a voltage change in the circuit. The phototube circuit is coupled to the 884V4 tube by condenser C. Thus, required voltage change ,is impressed on the grid of the 884-V4 tube to synchronize the sweep to the rotation of the part.

' The voltage for the phototube circuit is taken from the potentiometer circuit. consisting of resistors R1 and- R2. 'I'he phototube circuit consists of the phototube. resistance Ra, condenser C, and resistance R4 and is connected to the potentiometercircuit by double plugs I, 2, 3, 4. Resistance Ra is the load resistor which determines how great a voltage change will be eifected by a change .in illumination of the phototube. The condenser C couples the circuit to the 884-V4 tube. Resistance Ra is the leak resistance thatpermits the current to drain from the grid at a higher rate than it does through the-resistance Ra.

We claim:

1. In a machine for balancing rotors two upright mounting suspensions adapted to receive the bearings of the shaft of the rotor, one of said suspensionsbeing movable to enable the insertion and removal of the rotor, a track on the machine to receive the rotor preparatory to its insertion in the suspensions, a part of said track under the mounted rotor being movable to and from the rotor and being capable of being aligned with the remainder of' the track,means to cause the rotor to turn in its bearings in the suspensions, the mounting of the rotor in the suspensions permitting the rotor and its shaft to have a limited amount of bodily movement produced by the unbalance in the rotor, and means including movable probes mounted on the suspensions adapted to indicate the amountof movement. due to unbalance.

2. In a balancing machine, the combination of a pair of spaced supports adapted to receive the part to be balanced and permit rotation thereof, means at opposite ends of said part for removing material therefrom, a shiftable mounting for 'each of said means to permit it to be moved into and out of operative position, means for straddling the part and backing` it up while material is being removed therefrom, a shiftable mounting for said last-namedmeans to permit it to be moved in to and out of operative position, and means for interconnecting the shiftable mounting for said first-named means Vand the shiftable mounting for said backing up means to cause said backing up means to move to operative position when said material removing means is mo'ved to operative position.l

3. In a balancing machine the combination of a vpair of spaced supports adapted to receive'the part to be balanced and permit rotation thereof. means at the opposite ends of said part for removing material therefrom, a shiftable mounting for said means to pennit it to be moved into and out of operative position, means for straddling the part and backing it up while material is being removed therefrom, a shiftable mounting for said last-named means to permit it to be mov'ed into and out of 'operative position, and means for interconnecting said shiftable mountings to cause said backing-up means to move to operative position when said material removing means is moved to operative position, and means actuated by one of said shiftable mountings for disconnecting the drive for the part when the said means is moved to operative position.

4. In a balancing machine the combination of a support, a bearing xed to the support adapted to receive one of the journals of the body to be balanced, an assembly mounted on said support for movement toward and from said xed bearing, a bearing carried by said assembly in alignment with said fixed bearing and adapted to receive the other journal of said body,said support being provided with a flxed rest for said body adjacent one ot said bearings, a vertically movable rest mounted on said support between said bearings, said movable rest being normally valigned with the ixed rest, and means for raising said movable rest to align the journals of the body with said bearings to permit their insertion in said bearings.

5. In a balancing machine, a support having Aan arcuate supporting surface, a cylindrical bearing having limited rolling engagement with said surface, said bearing being adapted to receive withinit a journal of a body to be balanced, means for rotating the body `whereby in casenf unbalance therein said' bearing rolls back and forth on said surface, and means responsive to the movement of said bearing for indicating the rolling movement of said bearing in response to unbalance.

6. In a balancing machine, a pair of aligned arcuate supporting surfaces, a pair of cylindrical bearings each having rolling engagement with one of said surfaces, means for limiting rolling movement of said bearings on said surfaces, each of said bearings being adapted to receive within it a journal of a body to be balanced, means for rotating the body whereby incase of unbalance therein said bearings roll back and forth on said surfaces, and means responsive to the movement of one of said bearings for indicating the amount of rolling movement of said bearing in response to unbalance.

"l. In a balancing machine, a support having an arcuate supporting surface, a cylindrical bearing 91' Smaller radius than said surface, said bearing tating the body whereby in case of unbalance in said body said bearing rolls back and forth on said surface thereby affording an indication of unbalance, and means responsive to the move- Y,ment of said bearing for indicating the amount of rolling movement of said bearing in response to unbalance.

8. In a. balancing machine, the combination of a pairl of spaced supports having coaxial arcuate supporting surfaces. aligned antifriction bearings having cylindrical outer surfaces of smaller radius of curvature than said arcuate surfaces. said bearings each being in rolling engagement with one of said arcuate surfaces and being adapted to receive the journals of the body to be balanced, means for rotating the body whereby. in case of unbalance in said body, said bearings will roll back and forth on said arcuate surfaces thereby affording an indication of unbalance, and means responsive to the rolling movement of one of said bearings for indicating the amount of rolling movement of said one bearing in response to unbalance. f

9. In a balancing machine, a support having an arcuate supporting surface. an antifriction bearing having a cylindrical outer 4surface of smaller radius of curvature than said arcuate surface, said bearing being in rolling engagement with said arcuate surface and being adapted to receive a journal of the bodyto be balanced, means for movably supporting the other journal of said body, means for rotating the body whereby in case of unbalance in said body said bearing rolls back and forth on said arcuate surface,

and means responsive to the rolling movement of said bearing for indicating the amount of rollingmovement of said bearing in response to un` balance. g

10. In a balancing machine, a support having an arcuate supporting surface. an antifriction bearing having a cylindrical outer surface of smaller radius of curvature than said arcuate' means engaging said bearing and responsive to its l rolling movement for indicating" the amount of rolling movement of said bearing in response to unbalance, and stops on said support spaced from .said bearing and adapted to limit its rolling movement. THOMAS C. VAN DEGiRIFT. o y ANDREW W. zMUDA.

` EARL F. RIOPELLE.

' REFERENCES crrEn The following references are of record in the illev of this patent:

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